What would happen if the Av node delay were too long? and what happen if the delay were too Short?

If the AV node delay where too long the blood would be pumped into the ventricles before it could be pumped into the blood vessels, causing too much volume of blood to concentrate in the ventricles .  If the AV node delay were too short there would not be enough time for the blood to leave the ventricles before the next heart contraction.

Explanation:

your answer is "the 1950's"

answer; the tunica intima also called tunica interna, consists of elastic fibers,connective tissue and smooth muscle cells;